It has been observed through the analysis of stop-action photographs of the golf swing that during the down swing and principally just prior to contact between the club face and ball (hereinafter referred to as the "downswing"), the centrifugal forces that are generated by swinging the club are sufficient to cause the head of the wood to move off-center, relative to the ball, in the direction toward the plane of the shaft. Stated differently, as the club head approaches impact with the ball, its striking face should be generally square to the ball. A phenomenon called "dipping" alters this desired alignment by changing the vertical plane of the head and shaft so that the club head face (striking surface) and ball are not square at impact, the effect of which is to cause or contribute to an errant shot.
Dipping is believed to be the result of the centrifugal force caused by rotating the club head about a center of rotation. To better understand this concept and the effect produced thereby on the golf club during the portion of the swing from the top of the backswing through impact with the ball, consider that the center of gravity of a normal golf club head is off-set from the axis of the shaft and that during the downswing of the club, the center of gravity point of the head is urged to align itself with the axis of the shaft or the plane of the swing which is basically the same. In short, the head dips so that its center of gravity tends to align with the plane of the swing. As a result of these forces, the shaft bends out of its normal plane. FIG. 1 shows the golf club in an unaltered state at address. FIG. 2, shows the altered state achieved approximately at the ball contact point. As is shown in FIG. 2, the shaft is bending so that the center of gravity of the head is aligning with the plane of the swing. As can be seen, the head tilts at a slight angle which can substantially alter the flight of the ball and quality of the golf shot.
That the dipping phenomenon is not just a function of an individual's swing, has been confirmed by using a mechanical swing apparatus, known as the "Iron Byron" which reproducibly standardizes a golf swing and permits precise analysis of the structural effects on the head and shaft resulting from centrifugal forces throughout the swing. Measurements of the extent of the club head movement, measured vertically, and resulting from the centrifugal forces created during the swing have shown a change in the position of the head up to about one inch.
Applicants are not aware of any woods that are designed or include features that counteract the dipping effect. Golfers who are aware of dipping have sought to counteract the effect by positioning the club head above the ball at address, so that on impact with the ball the face of the club and the ball are substantially square. Of course, it requires considerable skill to make this adjustment to compensate for the dipping effect and the reproducibility factor, even for the good golfer, is far from satisfactory.
Applicants' invention contemplates a novel design modification of the head of a wood, which reduces or substantially eliminates the dipping effect by imparting "lift" to the head as it approaches impact with the ball.
While a review of the relevant prior art patents known to applicants reveals golf club head design features which tend to direct the flow of air in order to reduce air drag on the club and thereby to increase club head speed, none recognizes the dipping effect and none discloses or even suggests the objective of imparting "lift" to the club head. For example, U.S. Pat. No. 4,431,192 discloses the use of "vanes" attached to the head for directing the flow of air in a predetermined pattern to solve the problem of drag in a golf club driver. The patent further discloses that the vanes may be attached to the sole of the club and that they produce a "ram air exhaust effect".